Choosing the right heat pump for your building

Heat pumps extract heat from a natural or waste source, like, air, ground, water or waste heat.

A refrigeration cycle raises the temperature of the extracted heat. The heat is then transferred into a building through:

• radiators
• underfloor heating
• hot-water systems 
• air distribution systems

Heat pumps use electricity to move heat.

Air-source heat pumps:

• Extract heat from the outside air.
• Commonly configured as air-to-water systems in UK homes.
• Transfer heat into a wet heating system or hot-water cylinder.
• Require relatively little external space.
• Particularly suitable for densely developed sites.

In Tomorrow’s Energy Bean explains that air source is currently the dominant heat pump technology in the UK because of the density of buildings and limited availability of land.

Ground-source heat pumps:

• Extract heat from the ground.
• Can use, horizontal ground arrays, boreholes or aquifers.
• Transfer heat into a water-based heating system.
• Require more site-specific design and ground infrastructure than air-source systems.

Air-to-air heat pumps:

• Extract heat from outside air and deliver it directly into a building.
• Tends to be associated with air conditioning.
• Can provide both heating and cooling.
• Particularly relevant to commercial buildings such as offices and retail spaces.

In Tomorrow’s Energy Bean Beanland tell us that the appropriate technology depends on the characteristics of the site.

Key considerations include:

• available space
• local heat sources
• building heat demand
• existing heating systems
• required heating temperatures
• installation requirements
• capital cost.

For example, if you have limited space and air source may be most practical. However, if you have suitable land or ground conditions, a ground source may be viable. If you are near a river or water source, water-source systems could be considered. For large urban developments, larger heat pumps can potentially supply heat networks. See our case study on heat networks.

A heat pump should be designed around the building’s actual heat demand rather than simply replacing an existing boiler with an equivalent-sized unit. This will require a professional assessment.

Through this assessment, you need to take into account:

• building heat loss
• insulation and fabric performance
• room-by-room heating requirements
• radiator or underfloor heating capacity
• flow temperatures
• hot-water requirements
• heat pump sizing
• controls and commissioning.

Heat pumps can also form part of a wider electrified energy system, alongside solar PV, battery storage, thermal storage, electric vehicles and smart controls.

In our podcast Tomorrow’s Energy Bean Beanland, highlights the potential for these technologies to work together, with software managing when electricity is generated, stored and used. In fact, he says an electric vehicle could also potentially provide additional energy storage through vehicle-to-home technology.

• There is no single heat pump solution: technology selection should reflect the building and site.
• Air source is particularly versatile: limited space makes it a practical option for many UK buildings.
• Ground and water sources offer alternatives: particularly where suitable natural resources are available.
• Design determines performance: heat-loss calculations, system sizing and appropriate heat emitters are key.
• Lower temperature heating can support efficient operation.
• Heat pumps can operate alongside solar PV, batteries, thermal storage and EVs.